Compressor with cross axis

ABSTRACT

A multi-cylinder compressor of the nutating, or cam and wobble plate type, wherein the wobble plate is held against the cam rotor by a cross-axis mechanism that prevents rotation of the wobble plate while permitting its wobble, wherein all axial lost motion between the wobble plate and the cam is taken out by a continuous adjustable force transmitted through the cross-axis mechanism, preferably spring-maintained but capable of being positively and adjustably loaded, and wherein radial lost motion is prevented by design of the cross-axis mechanism.

United States Patent 1191 Mitchell 1451 Sept. 25, 1973 COMPRESSOR WITHCROSS AXIS [75] Inventor: Orville Mitchell, Star Harbor,

Tex.

[73] -Assignee: John E. Mitchell Company,

Dallas. Tex. [22] Filed: Jan. 18, 1972 [21] Appl. No.: 218,807

[52] U.S. Cl. 417/269 [51] 1m.c1 F04b 1/12 [58] Field of Search 417/269,270, 271;

[56] References Cited UNITEDSTATES PATENTS 3,552,886 1/1971o1s'on....;...i 417/269 3,018,737 l/l962 Cook et al.... 417/2693,455,585 7/l969 Raymond..... 417/269 3,257,960 6/1966 Keel 417/2693,082,693 3/l963 Budzich 417/270 3,663,122 7/1972 Kitchen 417/269Primary ExaminerWilliam L. Freeh Assistant ExaminerGregory LaPointeAttorney-Edmund C. Rogers [5 7] ABSTRACT A multi-cylinder compressor ofthe nutating, or cam and wobble plate type, wherein the wobble plate isheld against the cam rotor by a cross-axis mechanism that preventsrotation of the wobble plate while permitting its wobble, wherein allaxial lost motion between the wobble plate and the cam is taken out by acontinuous adjustable force transmitted through the cross-axismechanism, preferably spring-maintained but capable of being positivelyand adjustably loaded, and wherein radial lost motion is prevented bydesign of the crossaxis mechanism.

15 Claims, 11 Drawing Figures PAIENIEDsEPzswn Y SHEET 1 [IF 2 1COMPRESSOR WITH CROSS AXIS BACKGROUND AND OBJECTS OF THE INVENTIONHeretofore as, for example, in Olson U.S. Pat. No. 3,552,886, the wobbleor follower plate has been maintained against rotation in the housingeither by a pin and slot connection between the follower plate and thewall of the housing, or by a pair of intermeshing gearlike elements, onefixed to the housing and the other to the plate. Adjustments of theforce holding the parts together, to minimizelost motion and noise,involved screw means acting axially from the housing to the plate.Severe problems arose with such constructions, particularly because ofvibration and noise during operation of the compressor. It was found tobe extremely difficult to adjust and control the amount of lost motionand to provide a precisely smooth operation both with respect torotarymovements and rocking movements.

With the present invention, lost motion can be elimi nated by use ofcontinuously acting axially adjustable pressure-applying means, actingthrough a two-axis connection'between the housing and the followerplate.

Furthermore, the lostmotion adjustment in the geartype connector of thekind illustrated in the Olson patent could directly affect only theforce exerted by the wobble follower plate against the cam rotor,without adjusting the anti-rotation parts. In the applicant'sv device,the force controlling lost motion is transmitted throughout thecross-axis mechanism to the follower so that the working parts of thecompressor are stabilized by the single continuous axial thrust.

Since'the presentarrangement involves a type of cross-axis connectionpermitting the wobble plate to rock in any direction, the same mechanismcan be made to centralize the wobble follower on the cam rotor, preventrotation of the follower, and by an adjustably applied force, preventlost motion. The mechanism can be formed of parts that can be accuratelymachined to small tolerances at considerably less expense which is afurther advantage over the Olson construction.

The foregoing has been accomplished with the further advantages that thepiston rods move in radial planes only without significant peripheralmovement of the outer ends thereof. A contributing factor to this is themore favorable lever arm length in the present construction, coupledwith the lost motion take-up, as will be explained. This makes itpossible to have the most accurate positioning of each of the pistons atthe end of its compression stroke, thereby achieving the desiredcompression ratio with minimum tolerances. This is enhanced by the factthat the cross-axis connection permits the rocking movement to occurwith a minimum of peripheral oscillation of the cam follower plate. Thearrangement also permits the compressor to be made with the cylindersout of parallelism with the compressor' axis. g

The construction also makes possible the disposition of additional setsof cylinders radially outwardly from those illustrated and which wouldhave different strokes, an arrangement that is particularly applicableto multi-stage compressors.

Another feature of the present arrangement is that it is unnecessary tohave-a type of bearing at the center of the wobble plate such as isillustrated in the Olson patent to prevent lateral movement of thewobble plate. This advantage is obtained by the use of the cross-axisconstruction illustrated wherein the parts are so formed as to maintainthe plate centered on the machine axis and to prevent such lateralmovement. There are sufficiently close fits between the wobble plate andthe cross-axis portion that, while rocking movement can occur, lateraldisplacement is prohibited.

Other advantages will appear from the description to follow.

IN THE DRAWINGS FIG. 1 is a view of the power input end of thecompressor;

FIG. 2 is an opposite end view of the cylinder head of the compressor;

FIG. 3 is an enlarged diametrical section taken on the line 3-3 of FIG.1;

FIG. 4 is a transverse section on the line 4-4 of FIG.

FIG. 5 is an elevation of the cross-axis connections and wobble plate,taken from the spring cavity;

FIG. 6 is a sectional view of the universal movement mechanism andwobble plate taken on the line 6-6 of FIG. 5;

FIG. 7, is a reduced view of the wobble plate;

FIG. 8 is a sectional view through the wobble plate taken on the line8--8 of FIG. 7;

FIG. 9 is a diametrical section through' the wobble plate taken on theline 99 of FIG. 7 and enlarged;

FIG. 10 is an elevational view of the cross head; and

FIG. 11 is an edge view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The compressor housinggenerally indicated at has a medial cylindrical portion 21, with a powerinput end cover 22 at oneend secured to it as by screws. A cylinder head23 at the opposite end is likewise held on to the cylindrical portion 21by screws, and clamps a valve plate 24 between itself and the housing.

The input head 22' supports an input shaft 25 that is adapted to beconnected to a prime mover to be rotated thereby. An appropriate bearingand seal arrangement 26 provides for frictionless rotation of the shaft25 within the housing 20. The shaft 25 supports a cam rotor 28. Thisrotor has its back face (the left side in FIG. 3). perpendicular to theaxis of the shaft 25 and its forward surface at an angle thereto. Rollerthrust bearings 30 between the back surface of the rotor and the innersurface of the head 22 take up thrust load on the rotor 28 as willappear.

The main housing portion 21 has a solid portion 32 at its right end asappears in FIGS. 3 and 4, which has a plurality of cylinders 33 cuttherethrough. Centrally of this solid portion 32 of the housing 21 thereis a cylindrical bore 35 that receives the cylindrical shaft end 36 of ajoint holder or support member 37. The bifurcated head 38 of this member37 has a medial recess 39, and, as will appear more fully, is drilledacross to receive the ends of a rocking shaft.

' A cross head 41 has a first cross shaft or control shaft 42 that issnugly fitted into place in the cross head and held by a set screw 43.The shaft is rockably received in sleeve bearings 44 that are fixed inthe holes drilled across the bifurcated head 38 of the joint holdermember 37. The cross head 41 has shoulders or the like means 45 that fitclosely between and bear against the two bifurcations of the member 38or the two sleeve bearings 44 to reduce friction and yet to give asmooth operation with minimal end play or lost motion.

The cross head 41 also has, at ninety degrees to the shaft 42,projecting cylindrical oscillating shaft arms 48 having shoulders 49adjacent the body of the cross head. The two rocker arms 48 are receivedfor rocking movement in complementary semi-cylindrical grooves 50mounted in a wobble type follower plate 51. This plate has roller thrustbearings 52 to permit the cam roller to roll freely against thenon-rotatable follower plate 51 and rock it. The follower plate 51 has arectangular recess 53 against the sides of which the shoulders 49 engagewith a tolerance that permits free oscillation of the wobble plate butprevents radial movement of the follower plate.

The shaft 36 of the bifurcated support 37 is nonrotatably held in thecylindrical opening 35 by a key 54 anchored in the housing 21 that fitsin a keyway 55 in the shaft portion 36. This key keeps the bifurcatedmember 38, the cross head member 41, and the follower 51 from rotating,while permitting axial movement of the support 37.

The shaft portion 36 of the support 37 is bored out at 56 to receive acompression spring 57. An adjusting screw 58 is threaded into the end ofthis bore and preferably bears against the end of the spring 57 wherebyto apply a predetermined adjustable resilient force maintaining themember 38, the cross head 41, and the follower 51 and the rotor 28 in aclose interengagement. Lost motion at this point should be minimized.

While the spring 57 is preferably relied upon to maintain this force, insome cases a fixed-force may be applied by tightening the screw 58against the end of the support 37, usually without the spring 57, totake up lost motion between the cross-axis connections, the wobbleplate, and the cam and housing.

The follower 51 has a plurality of hemispherical sockets 60 illustratedin FIG. 9. These receive the ball ends 62 of piston rods 63. The outerrims of the socket 60 are swaged over the spherical ends 62 to preventwithdrawal of the balls 62 from the sockets.

In similar fashion, the other end of each piston rod 63 has a ballportion 65 fitted into a spherical socket of a piston 66. The walls ofthe sockets are bent over to prevent withdrawal of the balls once theparts are assembled. However, the ball and socket joints, when properlylubricated, are realtively friction-free.

There are a number of pistons 66 corresponding to the number ofcylinders 33, five being here illustrated, with their axes parallel tothe axis of the machine, this being the preferred arrangement.- Thesepistons move from positions illustrated in FIG. 3, where theircompression surfaces are coplanar with the ends of the cylinder housing21 to an opposite extreme. As is known in the art, and as illustrated inOlson U.S. Pat. No. 3,552,886, the cylinder head comprises the valveplate 24 together with the head 23. The cylinder head has a fluid inlet70 that opens into the inlet manifold 71, and through the valve plate 24into each cylinder. A reed valve 72 regulating the inlet passage isclosed in FIG. 3, and fluid previously drawn into the cylinder has beenexpelled through an outlet passage 76 past a reed valve 77 which now isopen. The compressed fluid is forced out through an outlet manifold 78,that receives compressed fluid from all of the cylinders and the fluidis finally discharged through a discharge passage 79. The othercylinders operate in like fashion.

ASSEMBLY AND OPERATION In assembling this compressor, it will be assumedthat the input head 22 is off. Before the pistons are installed, theshaft 36 of the bifurcated support 37 is inserted with the spring 57 inplace, and the cross-axis mechanism attached to the support. Asillustrated, the shoulders 45 hold the cross-head member with minimumtolerance between the arms of the bifurcated support 37 but in a mannerto permit free rocking movement of the cross head about the axis of thecross shaft 42, here called the control axis. The other cylindrical arms48 of the cross head 41 project at to the shaft 42.

After the foregoing, the pistons 66, attached to the follower plate 51,are all inserted in place with the proper rings or othercompression-retaining means. The follower is moved into position so thatits opposite grooves 50 receive the projecting rocker arms 48, in amanner to permit rocking movement of the wobble plate 51 about the axisof these arms 48, which axis is called the oscillating axis. Thereafter,the sub-assembly of the input head 22, drive shaft 25, and associatedparts, with the cam rotor 28, secured to the shaft 25 to rotatetherewith, are installed.

When this is completed, the adjusting screw 58 is turned until theproper force is applied to eliminate lost motion in the rocker assembly.Thereupon the valve plate and head 23 are installed with theirappropriate gaskets and sealing means and subassemblied so that thecompressor is ready to operate.

There is no circumferential lost motion, such as is inevitable in a gearor like arrangement, nor is there any problem of interengagement ofteeth, since all of the connections remain permanently made throughoutthe drive train.

As the cam rotor 28 is rotated by the shaft 25, its high portion nutatesthe wobble plate 51, causing the pistons to be successively forced'inand out, as known in the art. The reed valves also operate in the knownmanner, the total result being compressed fluid delivered successivelyfrom the five cylinders out the outlet 79.

In the foregoing action, the spring 57 adjusted by the screw 58 appliesforce against the support 37, urging it leftward in FIG. 3. The head 38of the support transmits this force to the pin 42 on the cross head 41,and by that member via the pins 48 to the plate 51; and any displacementof the cam 28 and input or drive shaft 25 is also taken up by forcing ofthe cam against the thrust bearing 30. Thus the single axially locatedmechanism regulates the pressure between all of the axially movableparts, centralizes and prevents rotation of the plate. Also there islittle lost radial motion through the mechanism, and the plate 51 isheld in position on the axis of the machine, and cannot slip radially,but has freedom to rock and operate the pistons.

As previously noted, lost motion, that can show itself in movement ofthe ends of the piston rods, and consequent variation in the compressionratio of the compressor, is reduced by this cross-axis construction,owing to the favorable leverage of the cross axis arrangement and thelost motion take-up. In former constructions, the lost motion take-up isapplied very near to or at the axis of the wobble plate as by aball-andsocket connection between a thrust member and the wobble plate,and the lost motion at that point of takeup is multiplied out at theends of the piston rods.

The cross-axis mechanism hereof provides at least twice as much leverarm length as the prior art, since the lost motion take-up by the spring57 or the shaft 36 is applied through the bifurcated arms of the head 38and the shafts 42 and 48, quite some distance from the axis. Also veryclose tolerances can be maintained in the shaft bearings, which can beheld to closer tolerances than ball-and-socket joints.

With a predetermined lost motion tolerance at an axial point of take-up,such as at the ball 71 of 94 of the Olson patent, there can be aconsiderable multiplication of that tolerance at the location of thepiston rod connections 54 or 112. In the present case, the same lostmotion at the ends of the cross axis arms 42 and 48, by geometry,permits only a fraction of the multiplication occuring in Olsonsconstruction. And the cylindrical bearing construction reduces theamount of initial lost motion.

As a result, the amount of noise generated in the present cross-shaftarrangement is minimal, and the variation in compression ratio isbrought down substantially to zero.

Various changes and modifications may be made within this invention aswill be readily apparent to those skilled inthe art. Such changes andmodifications are within the scope and teaching of this invention asdefined by the claims appended hereto.

What is claimed'is:

1. In a nutating compressor or like machine of the type having ahousing, adrive shaft passing through the housing, a sloping cam on thedrive shaft inside the housing and rotated by the shaft, a wobble platenutated by the rotation of the cam and at least one piston reciprocatedwithin a cylinder in the housing by the plate; the combinationof: ajoint support in axial alignment with the cam on the input shaft,mounted in the housing; a cross-axis member, means mounting thecross-axis member on the support for rocking movement about a controlaxis transverse to the cam axis, said means preventing rotation of thecross-axis member relatively to the support about the cam axis; connections between the wobble plate and the cross-axis member providingrocking movement of the plate relatively to the cross-axis member aboutan oscillating axis at right angles to the control axis; means to holdthe joint support against rotation. in the housing; and thereby holdingthe cross-axis member and wobble plate against rotation relatively tothe housing; and means to fix the position of the joint support axiallyin the housing to prevent axial lost motion in the several movableinterconnections between the joint support, the cross-axis member andthe wobble plate.

2. The combination of claim 1, with frictionless thrust bearings betweenthe cam and the wobble plate.

3. The combination of claim '1 wherein the lastnamed positioning meansincludes an unyieldable adjusting device to fix the position of thejoint support in the housing.

4. The combination of claim 1, with means to prevent radial movementbetween the cross-axis member and the joint support and between thecross-axis member and the wobble plate.

5. The combination of claim 1, wherein the means mounting the cross-axismember on the support comprises a rock shaft device extendingtransversely to the axis of the cam and a journal bearing device toreceive the cross shaft for rocking movement, one of said devices beingon the support and the other device being on the cross-axis member.

6. The combination of claim 5 with means to prevent radial lost motionbetween the joint support and the cross-axis member.

7. The combination of claim 5, wherein the joint support has oppositeradially extending arms, the crossaxis member being disposed betweenthem, and radially extending rock shaft means between the cross-axismember and the arms, the arms embracing the crossaxis member with a fitthat permits free rocking movement but prevents relative radial movementbetween these parts.

8. The combination of claim 1, wherein the connection between the wobbleplate and cross-axis member includes a radially extending rock shaftdevice and a radially extending bearing device for the rock shaft, oneof said devices being on the wobble plate and the other on thecross-axis member.

9. The combination of claim 8, with a recess in the wobble plate toreceive the cross-axis member, the parts having a close fit to permitfree rocking movement but to prevent radial lost motion between them.

10. The combination of claim 1, wherein the joint support has an axialshaft disposed in an axial socket in the housing, and has a bifurcatedfree end toward the cam, a control shaft mounted in the bifurcations andthe cross-axis member to provide rocking of the crossaxis member aboutan axis transverse to the cam axis, the cross-axis member having secondrock shaft means projecting from it along an oscillating axis at rightangles to the control shaft, the wobble plate having recesses to receivethe rock shaft means to permit rocking of the plate about theoscillating shaft.

11. The combination of claim 10, wherein the wobble plate has a centralrecess into which the cross head fits with the rock shaft meansextending therefrom to engage the plate radially outwardly from thecross head.

12. The combination of claim-l2, with means engaging the end of thejoint support for displacing it in its socket toward the wobble plate,thereby to take upv lost motion in the connection.

13. The combination of claim 12, wherein the engaging means includes aspring acting against the end of the joint support and against meansfixed to the compressor housing.

14. In a nutating compressor having a housing, a plurality of pistonsand piston rods in the front end of the housing, a drive shaftjournalled through the rear of the housing; a rotor cam on the shaft, awobble plate follower adapted to receive the piston rods, anti-frictionmeans for the cam and follower including axial thrust bearing means, anaxially slidable non-rotatable joint support on the housing, means forproviding rearward axial thrust on the joint support; andtwo-axis meansbetween the support and the wobble plate follower, said two-axis meansbeing disposed to receive the rearward axial thrust of the meansproviding same on the joint support, and to transmit the thrust throughto the follower, the two-axis means also providing for the rockingmovement of the follower but preventing rotation thereof relative to thepiston rods.

15. The combination of claim 14, wherein the twoaxis means includesabutting shoulders adjacent the axes to prevent radial displacement ofits parts and the follower, while it transmits the non-rotation andrearward axial thrust.

1. In a nutating compressor or like machine of the type having ahousing, a drive shaft passing through the housing, a sloping cam on thedrive shaft inside the housing and rotated by the shaft, a wobble platenutated by the rotation of the cam and at least one piston reciprocatedwithin a cylinder in the housing by the plate; the combination of: ajoint support in axial alignment with the cam on the input shaft,mounted in the housing; a crossaxis member, means mounting thecross-axis member on the support for rocking movement about a controlaxis transverse to the cam axis, said means preventing rotation of thecross-axis member relatively to the support about the cam axis;connections between the wobble plate and the cross-axis member providingrocking movement of the plate relatively to the cross-axis member aboutan oscillating axis at right angles to the control axis; means to holdthe joint support against rotation in the housing; and thereby holdingthe cross-axis member and wobble plate against rotation relatively tothe housing; and means to fix the position of the joint support axiallyin the housing to prevent axial lost motion in the several movableinterconnections between the joint support, the cross-axis member andthe wobble plate.
 2. The combination of claim 1, with frictionlessthrust bearings between the cam and the wobble plate.
 3. The combinationof claim 1 wherein the last-named positioning means includes anunyieldable adjusting device to fix the position of the joint support inthe housing.
 4. The combination of claim 1, with means to prevent radialmovement between the cross-axis member and the joint support and betweenthe cross-axis member and the wobble plate.
 5. The combination of claim1, wherein the means mounting the cross-axis member on the supportcomprises a rock shaft device extending transversely to the axis of thecam and a journal bearing device to receive the cross shaft for rockingmovement, one of said devices being on the support and the other devicebeing on the cross-axis member.
 6. The combination of claim 5 with meansto prevent radial lost motion between the joint support and thecross-axis member.
 7. The combination of claim 5, wherein the jointsupport has opposite radially extending arms, the cross-axis memberbeing disposed between them, and radially extending rock shaft meansbetween the cross-axis member and the arms, the arms embracing thecross-axis member with a fit that permits free rocking movement butprevents relative radial movement between these parts.
 8. Thecombination of claim 1, wherein the connection between the wobble plateand cross-axis member includes a radially extending rock shaft deviceand a radially extending bearing device for the rock shaft, one of saiddevices being on the wobble plate and the other on the cross-axismember.
 9. The combination of claim 8, with a recess in the wobble plateto receive the cross-axis member, the parts having a close fit to permitfree rocking movement but to prevent radial lost motion between them.10. The combination of claim 1, wherein the joint support has an axialshaft disposed in an axial socket in the housing, and has a bifurcatedfree end toward the cam, a control shaft mounted in the bifurcations andthe cross-axis member to provide rocking of the cross-axis member aboutan axis transverse to the cam axis, the cross-axis member having secondrock shaft means projecting from it along an oscillating axis at rightangles to the control shaft, the wobble plate having recesses to receivethe rock shaft means to permit rocking of the plate about theoscillating shaft.
 11. The combination of claim 10, wherein the wobbleplate has a central recess into which the cross head fits with the rockshaft means extending therefrom to engage the plate radially outwardlyfrom the cross head.
 12. The combination of claim 12, with meansengaging the end of the joint support for displacing it in its sockettowarD the wobble plate, thereby to take up lost motion in theconnection.
 13. The combination of claim 12, wherein the engaging meansincludes a spring acting against the end of the joint support andagainst means fixed to the compressor housing.
 14. In a nutatingcompressor having a housing, a plurality of pistons and piston rods inthe front end of the housing, a drive shaft journalled through the rearof the housing; a rotor cam on the shaft, a wobble plate followeradapted to receive the piston rods, anti-friction means for the cam andfollower including axial thrust bearing means, an axially slidablenon-rotatable joint support on the housing, means for providing rearwardaxial thrust on the joint support; and two-axis means between thesupport and the wobble plate follower, said two-axis means beingdisposed to receive the rearward axial thrust of the means providingsame on the joint support, and to transmit the thrust through to thefollower, the two-axis means also providing for the rocking movement ofthe follower but preventing rotation thereof relative to the pistonrods.
 15. The combination of claim 14, wherein the two-axis meansincludes abutting shoulders adjacent the axes to prevent radialdisplacement of its parts and the follower, while it transmits thenon-rotation and rearward axial thrust.